AAV/Studor noise

I just removed the wall above the kitchen sink and replace the 1.5" pvc vent stack with a studor inside the wall behind the kitchen sink. It drains fine but makes a light thumping noise as the water drains from either the sink or the dishwasher. This same drain line has a utility sink installed in the bottom floor which also has a studor vent inside the sink cabinet but it does not make noise. All drains flow smoothly with no odor but the one behind the sink just makes noise inside the wall where the studor was installed. I'm concerned that the valve may be faulty. The wall is already capped with a bar so it would be difficult to repair inside the wall. Please advise...
Thanks

An AAV inside the wall requires an access panel for replacement purposes.

Code requires the AAv MUST be installed where it can be serviced (i.e., not capped in a wall). It may be the pipe moving, not the AAV. The only moving part in there is a rubber diaphram. An AAV will only let air in, and a dishwasher can pump some water fairly quickly, so it could be trying to push air out the AAV, and it should prevent that. If you had an atmospheric vent and took it out, the inspector here would have given you major grief.

Are we reading this right?You removed a good vent and put in an AAV?Why?
The noise you may be hering is the AAV letting air in when things are draining.

Yes I removed the good vent and replaced with the SSV b/c I removed the wall. I did not put in an access panel for the vent but I will when I replace the cabinets. I will probably just move the vent under the sink and cap the pipe inside the wall. That will make for easier access. Is it common to hear these vents?

They do make noise...
Sometimes they sound like somebody been eating beans!